1. Field of the Invention
The present invention relates to the purification of water, particularly potable waters, and, more especially, to water purification by flocculation, utilizing as the flocculant therefor, a certain composition of matter comprising a water soluble natural or synthetic gum or polymer, or a water soluble biogum.
2. Description of the Prior Art
It is known to this art to purify/treat various waters and sludges by flocculation, employing as the flocculating agent therefor certain metal salts, such as CaCl.sub.12, FeCl.sub.2, FeCl.sub.3, FeSO.sub.4 or Fe.sub.2 (SO.sub.4).sub.3, or admixtures thereof, as described in French Pat. No. 1,399,351.
Aluminum sulfate is also frequently used. It too is known, however, that in flocculation two phenomena are typically superimposed upon one another: on the one hand, the neutralization of charges and, on the other, the agglomeration of neutralized particles in more or less large floccules. Aluminum sulfate and the different iron compounds typically give rise only to the first phenomenon and yield only small floccules, which are slowly decanted. The known flocculating additives, thus, do not always provide a precipitate with the properties required for effective and facile decantation.
And it is for this very reason that the natural gums are used individually, or in combination with inorganic salts (potato starch, alginates, dextrins, gelatin); also, certain water soluble, high molecular weight synthetic polymers/gums too may be employed as flocculating agents.
Said polymers/gums may be obtained either by complete chemical synthesis, such as, for example, the polyacrylic acids or the polyacrylamides, or by biosynthesis, such as, for example, Xanthan gum produced by the fermentation of a carbohydrate with bacteria of the genus Xanthomonas. As an illustration of the use of Xanthan gum in the purification of waters, compare published French application No. 78/36644.
The difficulty encountered in the employment of most of the aforesaid polymers/gums as flocculating adjuvants, however, is that they are difficult to solubilize, which flies in the face of their use as flocculating additives.
One of the major problems in the treatment/purification of waters further consists of the fact that the nature of the waters to be treated varies greatly from one location to another, and even in the same location from one day to the other, such that a solution that is effective for one type of water, cannot be used when conditions change.
Serious need thus exists in this art for a solution to the problem of the desirable use of gums as flocculating adjuvants, and to find a solution that is universally applicable, regardless of the nature of the waters to be treated/purified.